Now, another group of compounds that I personally have attached considerable importance to, as a biochemist, influenced by my hero, Fritz Lipmann, by others, Ef Racker, Fitzi Lynen, and people who worked on these compounds and identified the first catalyst involved, the thioesters, compounds between acids and thiols – thiols being sulphur compounds analogous to alcohols. And the thioesters bond is one again of the key bonds in life today – that is, it is involved in some of the most central mechanisms of energy transfer again in the so-called substrate level of phosphor relations and the thioester bond is involved in a very large number of bio synthetic mechanisms and some of the coenzymes involved in those have relatively simple structures. Coenzyme A... coenzyme A is made up of two compounds, AMP or phosphor AMP, and... phosphopantetheine and phosphopantetheine is made of three very simple compounds that can all arise spontaneously and condense spontaneously to pantethine under conditions that... sorry about that... conditions that have been reproduced by Stanley Miller and his co-workers, and the other coenzyme involved in thioester based reactions is echoic acid – octanoic acid. Now, octanoic acid is an even simpler molecule. It's just an eight carbon acid with two thiols on two not adjacent, but almost adjacent, carbon atoms. So it's a very simple molecule. Could very well... nobody's made it in the lab, but it could very well arise spontaneously in a volcanic environment again, because thioesters and thiols are derivatives of hydrogen sulphide, and anybody who has visited a volcanic area – whether it's Mount Fuji in Japan or the Yellowstone Park or volcanoes in New Zealand, whatever – will remember the smell. Volcanic vapours smell like rotten eggs and the smell of rotten eggs is due to hydrogen sulphide. So hydrogen sulphide, sulphur compounds, again are most probably most abundant in a volcanic environment. So I see... I tend to see as a biochemist that pyrophosphates and thiols and thioesters, products of... possible products of a volcanic environment may have played a very... a key role in the origin of life similar to the role that they are playing today. And this is a little different from what chemists... or the more organically-minded would tend to believe. They say, 'Well, this is impossible because the reactions in which these compounds participate could not arise without... without enzymes. And enzymes came with proteins, therefore after RNA, so they couldn't have been enzymes there.' And that's my only little original suggestion here, in addition to insisting on the thioesters; my suggestion is that, yes, those reactions could not have taken place without... without a catalyst. Everybody realises that, and all the experts working in this field are looking for catalysts, but they're looking for mineral catalysts. A lot of work has been done with clay, molecules of clay, and metals. Metals are quite important. And so my suggestion has been that, yes, mineral catalysts, metals, have been very important, but perhaps more important were peptides.